Recently, thanks to amazing performance enhancement of network devices and portable digital or telecommunications devices, telecommunications between two distant locations can be done more and more easily and efficiently year after year. Among other things, visual information conveyance means have developed so rapidly these days that high-definition digital cameras and big-screen display monitors are now available almost everywhere to provide everyone around the globe with highly realistic visual information, no matter where he or she is located. In the meantime, the performance of audio information conveyance means have also been enhanced so astonishingly nowadays that multi-channel reproduction and other techniques now realize wide-range sound field control. Consequently, by making full use of these cutting-edge audiovisual technologies in combination, audiovisual communications with a lot of presence have been spreading more and more extensively these days particularly in the fields of entertainments and business.
And to further increase user's sensation of reality and presence, means for conveying not just such visual or audio information but also any other kind of information that would excite all of the five senses of a human being have been researched and developed extensively lately. That is to say, technologies for conveying or reproducing a feel, a smell or even a taste have been developed actively by a lot of people.
The sense of touch is used by a person who tries to get a feel of something, and he or she may get a “hard/soft feel” or a “smooth/rough feel” by sensing its hardness or surface property. The sense of sight or hearing is a non-contact type sense of a person who has received a light wave or an acoustic wave, whereas the sense of touch is a contact type sense that is not used by a person until he or she actually touches something. That is why if such tactile information conveyance means is combined with the conventional audiovisual information conveyance means, the sensation of reality and presence could be improved by leaps and bounds.
However, to enable a network device or telecommunications device to convey or reproduce the feel that a person has gotten by touching something, the following three major functions need to be realized:                (1) tactile quantification,        (2) tactile sensing, and        (3) tactile display        
As disclosed in Non-Patent Document No. 1, for example, the tactile quantification can be done by making not only a sensory evaluation to collect data about a person's sensory response but also a factor analysis for representing the feel as numerical values by analyzing the data collected.
The sensory evaluation can be made by presenting a questionnaire sheet 1501 as shown in FIG. 2 to a subject under test who has touched something and having him or her rate his or her feel by numerical values in response to each question, which consists of two adjectives with opposite meanings. Thus, the subject under test needs to tell his or her hard or soft feel by any of the given seven ratings, for example.
According to Non-Patent Document No. 1, the subject under test was made to answer his or her feel of 20 kinds of objects in response to 12 different questions. On the other hand, the factor analysis is a technique for making a multivariate analysis for analyzing respective elements on the supposition that the data observed is a synthetic quantity. Specifically, according to Non-Patent Document No. 1, a result of each sensory evaluation can be summarized into the four factors representing a rough feel, a cold/hot feel, a dry/wet feel, and a hard/soft feel, respectively. That is why the subject's feel can be described quantitatively as a tactile feature quantity vector 1602 in a four-dimensional feature quantity space 1601, of which the four axes are represented by those four factors, as shown in FIG. 3. The tactile feature quantity vector 1602 is a person's quantitative response characteristic that has been obtained through the sensory evaluation experiment and corresponds to a psychological quantity.
As disclosed in Non-Patent Document No. 2, for example, tactile sensing can be done by associating an object's physical property value with the tactile feature quantity vector. The object of Non-Patent Document No. 2 is to make an objective evaluation of a piece of cloth's handling. As represented by the following Equation (1), the handling characteristic Hk of a piece of cloth is represented by making a linear combination of the cloth's dynamics and surface physical property xi:
                              H          k                =                              C                          k              ⁢                                                          ⁢              0                                +                                    ∑                              i                =                1                            16                        ⁢                                                  ⁢                                          C                ki                            ⁢                                                                    x                    i                                    -                                                            x                      _                                        i                                                                    σ                  i                                                                                        (        1        )            where xi is one of 16 different kinds of physical measured values including a tensile property value, a bend property value, a shear property value, a compression property value, a surface property value, a thickness property value and a weight property value; Hk is one of 5 different kinds of handling characteristic values consisting of stiffness, smoothness, fullness with softness, crispness and anti-drape stiffness; the over-barred xi represents the average of multiple samples; σ i is the standard deviation of the multiple samples; and Ck0 and Cki are constants. The constants Ck0 and Cki are calculated by carrying out a regression analysis on the cloth's dynamics and surface property xi obtained from a number of cloth samples and the handling characteristic Hk. The cloth's dynamics and surface property xi are obtained by putting the object into an instrument and by measuring the target physical property value with the object deformed if necessary (i.e., a tensile, bending, shear or compressive stress applied thereto) by the instrument. As in Non-Patent Document No. 1, the handling characteristic Hk is also determined by making the subject under test feel the object of a sensory evaluation experiment and answer a tactile intensity that he or she has gotten on a texture basis. The processing step of calculating the constants Ck0 and Cki is a so-called “learning processing step” and Equation (1) is perfected by finishing this processing step. After that, the process advances to a “performing processing step” in which the cloth's dynamics and surface property xi of an unknown object are measured and the handling characteristic Hk is estimated by Equation (1). The handling characteristic Hk is also a person's quantitative response characteristic that has been obtained through the sensory evaluation experiment and corresponds to a psychological quantity, too. Consequently, Equation (1) is a physical-psychological transformation equation for use to transform a physical quantity into a psychological quantity and can be used in this example to transform a physical quantity representing the cloth's dynamics and surface property xi into a psychological quantity representing the handling characteristic Hk.
FIG. 4 is a block diagram illustrating the flow of a conventional process including the tactile quantification and sensing processing steps described above. In the learning processing step 1701, the feel of a subject under test 1703 is represented quantitatively using a number of objects 1702 of learning. The subject under test 1703 answers his or her feel of the objects 1702 of learning using sensory evaluation means 1704. Then, his or her answer is subjected to a multivariate analysis, and has its factors analyzed, by factor analyzing means 1705. As a result, a group of those factors is output as a learning material tactile feature quantity vector F. In this case, the tactile feature quantity vector 1602 shown in FIG. 3 and used to describe Non-Patent Document No. 1 corresponds to the learning material tactile feature quantity vector F shown in FIG. 4. Also, in this learning processing step 1701, the physical property values of the multiple objects 1702 of learning are measured by an object physical measuring section 1706. And a result of this measurement is output as a learning material physical property value vector Ps. The cloth's dynamics and surface property xi represented by Equation (1) and used to describe Non-Patent Document No. 2 correspond to the learning material physical property value vector Ps shown in FIG. 4. Physical-psychological transformation calculating means 1707 calculates a function M for transforming the learning material physical property value vector Ps into a learning material tactile feature quantity vector F by the following Equation (2):F=M(Ps)  (2)
The means for calculating the constants Ck0 and Cki of Equation (1), which has been used to describe Non-Patent Document No. 2, corresponds to the physical-psychological transformation calculating means 1707. In general, a matrix is used as the function M, and Equation (2) becomes a matrix transformation equation. On the other hand, in the performing processing step 1708, an object under test 1709, which needs to be subjected to a tactile measurement, has its physical property value measured by an object physical measuring section 1706 to obtain a reference material physical property value vector Pt. Using the function M that has been calculated in the learning processing step 1701, a physical-psychological transformation section 1710 transforms the reference material physical property value vector Pt into an estimated tactile feature quantity vector F′ by the following Equation (3):F′=M(Pt)  (3)
As disclosed in Non-Patent Document No. 3, the tactile display can be done by getting the person's skin deformed by an actuator to make him or her have some feel. According to Non-Patent Document No. 3, an ultrasonic vibrator is used as the actuator and a rough feel and a hard/soft feel are controlled by making use of the squeezing effect produced by the ultrasonic vibrator. As used herein, the “squeeze effect” refers to a phenomenon that pressure is generated in a fluid between two objects that are rapidly approaching each other, and produces a hydrodynamic lubrication effect.
FIG. 5 illustrates the configuration of a tactile display section 1801 and also shows its correlation with a rough feel 1803, a hard/soft feel 1804 and a frictional feel 1805, which are all feels of a person's 1802. The tactile display section 1801 contacts and interacts with the person's finger. In FIG. 5, a part where the tactile display section 1801 and the person 1802 cause interaction is called an “interaction part 1806” which is surrounded with a dashed rectangle.
To present the rough feel 1803 to him or her, the tactile display section 1801 excites the person 1802 with vibrations 1807. In this case, the vibrations 1807 are generated as the sum of the steady-state components 1813 and non-steady-state components 1809 of the amplitude modulation of an ultrasonic vibration section 1808. However, since the non-steady-state components of the amplitude modulation wave would be sensed to be unevenness, of which the height is several ten times as large as the amplitude of the vibrations, the rough feel 1803 is controlled with the non-steady-state components 1809. Also, the higher the velocity of a finger that feels the unevenness of the object, the higher the frequency of vibrations to be transmitted to the finger. Conversely, the lower the velocity of the finger that feels the unevenness of the object, the lower the frequency of vibrations to be transmitted to the finger. That is to say, as the frequency of vibrations to be transmitted to the person's finger is proportional to the velocity of his or her finger, the finger velocity 1810 is measured by a position sensor section 1811 and used to control the non-steady state components 1809.
Also, to display the hard/soft feel 1804 to him or her, the tactile display section 1801 excites the person 1802 with a force distribution 1812, which can be controlled using the steady-state components 1813 of amplitude modulation of the ultrasonic vibration section 1808. However, as described above, the steady-state components 1813 also affect the vibrations 1807. That is why by adjusting the ratio of the amplitude of the steady-state components 1813 to that of the non-steady-state components 1809, influence on the rough feel 1803 can be corrected.
Furthermore, to display the frictional feel 1805 to him or her, the tactile display section 1801 excites the person 1802 with frictional force 1814. Since the squeeze effect produced by the ultrasonic vibrator decreases the coefficient of friction, it is difficult to control the frictional feel independently using only the ultrasonic vibrator. For that reason, the variation in the friction characteristic of the ultrasonic vibrator is corrected by getting a tangent line force 1816 displayed by a force sense displaying section 1815. The tangent line force 1816 is calculated based on the finger velocity 1810 and finger position 1817 that have been detected by the position sensor section 1811 and the person's finger's normal force 1819 that has been detected by a force sensor section 1818. Specifically, first, right after the tactile display section 1801 and the person 1802 have contacted with each other, static frictional force, which has been calculated based on the magnitude of shift from the initial point of contact, is displayed. But if the ratio of the tangent line force displayed to the normal force that has been applied to the tactile display section exceeds the static friction coefficient displayed by the force sense displaying section 1816, kinetic frictional force is displayed to the person 1802.
In this manner, the tactile display section 1801 uses the ultrasonic vibration section 1808 and the force sense displaying section 1815 to excite the person 1802 with the vibrations 1807, the force distribution 1812 and the frictional force 1814, thereby displaying the rough feel 1803, the hard/soft feel 1804 and the frictional feel 1805 to the person 1802. In this case, since the coefficient of friction decreases due to the squeeze effect produced by the ultrasonic vibrator, it is difficult to control the frictional feel by using only the ultrasonic vibrator. For that reason, the frictional feel is corrected with the tangent line force 1816 produced by the force sense displaying section 1815. The tangent line force 1816 is calculated based on the finger velocity 1810, the finger position 1817 and the normal force 1819 that have been obtained by the position sensor section 1811 and the force sensor section 1818.
FIG. 6 is a block diagram illustrating a tactile processor 2100, which is tentatively obtained by the present inventors by virtually combining the tactile quantification and sensing scheme that has already been described with reference to FIG. 4 with the tactile display scheme that has just been described with reference to FIG. 5.
The tactile sensor section 2101 is the same as the one shown in FIG. 4 and the object physical measuring section 1706 calculates a physical property value of the object under test 1709 and outputs the reference material physical property value vector Pt. The physical-psychological transformation section 1710 has already gotten the function M for use to perform a physical-psychological transformation through the learning processing step 1701 shown in FIG. 4 and transforms the reference material physical property value vector Pt into the estimated tactile feature quantity vector F′. The tactile display section 1801 is designed to make the person 1802 touch an actuator section 2102 and have a feel. The actuator section 2102 corresponds to the combination of the ultrasonic vibration section 1808 and force sense displaying section 1815 shown in FIG. 5. An actuator control section 2103 drives the actuator section 2102. The actuator control section 2103 corresponds to the electrical means for vibrating the ultrasonic vibration section 1808 and electrical means for driving the force sense displaying section 1815 which are shown in FIG. 5.
A psychological-physical transformation section 2104 transforms the estimated tactile feature quantity vector F′ into an actuator control signal D′ so that the feel that has been gotten by the tactile sensor section 2101 can be reproduced by the tactile display section 1801. Such a transformation can be represented by the following Equation (4):D′=Q(F′)  (4)where the function Q is a psychological-physical transformation function for use to transform the estimated tactile feature quantity vector F′, which is a psychological quantity, into the actuator control signal D′, which is a physical quantity. This function Q is determined by the input and output characteristics of the tactile display section 1801. That is to say, this function Q is determined by the relation between the actuator control signal D′ to be input to the tactile display section 1801 and the person's feel Fo to be output from the tactile display section 1801. Such a relation is represented by the following Equation (5):FO=V(D′)  (5)
The function V corresponds to the input and output characteristics of the tactile display section 1801. The inverse function of Equation (5) is equivalent to Equation (4). That is why Equation (4) can be rewritten as follows:D′=V−1(F′)  (6)
That is to say, if the estimated tactile feature quantity vector F′ is transformed with the input and output characteristics V−1 of the tactile display section 1801, the actuator control signal D′ to make the person 1802 have a feel on the object under test 1709 can be calculated.
By detecting the feel that a person has when touching something as described above, a tactile feature quantity vector can be obtained and transmitted over a network. As a result, that feel can be reproduced on a tactile display.